Oil diffusion pump with splash boiler



Jan. 9, 1968 A. A. LANDFORS 3,

OIL DIFFUSION PUMP WITH SPLASH BOILER Filed Aug. 25, 1966 United States Patent 3,362,623 OIL DIFFUSION PUMP WITH SPLASH BOILER Arthur A. Lautlfors, Sharon, Mass, assignor to National Research Corporation, Newton, Mass., a corporation of Massachusetts Filed Aug. 23, 1966, Ser. No. 574,433 6 Claims. (Cl. 230-101) The present invention relates to fractionating oil diffusion pumps constructed from metals like stainless steel which are easy to clean and maintain, but unfortunately ditficult or expensive to fabricate in conventional diffusion pumps.

One of the most expensive items in a modern stainless steel dilfusion pump is the boiler plate, including fractionating fins on top and precise finish grinding on bottom to mate with a heater element. The conventional vapor jet assembly with its fractionating tube and splash bafile are also much more expensive to fabricate in stainless steel than in aluminum or mild steel.

It is the object of the invention to provide a new type of fractionating oil pump which aifords economy of construction consistent with high speed and throughput and low blankoff and backstreaming. The economy of construction is such that the pump is less expensive in stainless steel than a conventional aluminum or mild steel pump while affording almost equal running performance and the maintenance advantages of stainless steel or the like.

The new pump comprises a pump with a simple boiler well and an economical rod heater disposed within the well. Disposed just above the well is a splash tray which catches oil splash from violently boiling oil in the well. The splash from the well also strikes the bottom of the tray to keep the carryover oil in the tray boiling.

The invention will be more readily understood from the following description taken in connection with the single figure of drawings which is a cross-sectional representation of a preferred embodiment of the invention.

Referring now to the drawing, the pump 10 comprises a vertically arranged tubular body 12. The body is cooled by water coils (not shown) soldered to it or a fan (not shown) which blows air over it. The pump inlet is shown at 14 and the foreline exit at 16. A baffle 18 is provided at the inlet. Within the pump body is the conventional vapor jet assembly 20 with a series of nozzles 22, a fractioning tube 24, and a tie-down rod 26. Oil is boiled within the vapor jet assembly in a boiler arrangement described below. The boiled off vapor exits from the nozzles in streams which reach the cooled wall 12 and condense to return to the interior of the vapor jet assembly through a barometric oil seal 28.

The boiler 30 of the pump comprises a well 32 made by simply welding a metal bottom cap 34 to the bottom of the pump body 12. No special finish of the cap 34 is required. A pool of oil 36 is contained in the boiler. The heater comprises a commercial 450 watt electric rod heater 38 fitting through a finned tube 40. The tube is located below the minimum level of the oil pool 36 and passes completely through the pump body 12 to expedite removal and insertion of heater 38. The boiler also comprises a splash catch tray 42 positioned just above the oil pool 36. The tray has an annular vertical side wall 44 which, together with the tray 42, acts as a splash bat-fie. Holes 46 are drilled in the side wall 44 to provide a passage to the tray. The oil in pool 36 boils violently and a portion of it as indicated by arrows 48 splashes over into the tray 42 via holes 46. A portion of the splash indicated by arrows 50 continually strikes the underside of tray 42 so that the secondary oil collected in the tray is maintained at essentially the same temperature as the oil pool 36. A fiared out extension 52 of the fractionating tube 12 reaches down to the tray and encloses a portion of the oil in tray 42 so that vapors from it go up the fractionating tube as indicated by arrows 54. The outer portion of oil in the tray also boils and those vapors indicated by arrows 56 go to all the nozzles 22, except for the topmost nozzle. A- substantial flow of vapor, indicated at 58, goes directly from the oil pool 36 to the lower nozzles.

In operation the temperature of the tube 40 is about 550 F. There is a substantial temperature drop across the surface layer of oil at the fins so that the oil pool runs at about 420 F. The splash tray 42 and its collected oil also run at about 420 F. Typically, the pump body has a 3 /2 inch diameter, the splash tray has a 2 /2 inch diameter (the portion circumscribed by tube 52 being 2 inches), and twelve inch diameter holes are provided as holes 46.

The splash tray is heated sufiiciently by splash (arrows 50) that a strong top jet through the top nozzle 22 is assured. The splashing which refills tray 42 assures a continuous substantial supply of oil. Trapped gases in the carryover are boiled off before the oil in tray 42 enters the central fractionating portion.

Thus I have provided a stainless steel fractionating diffusion pump which incorporates an economical rod heater. Because of the stainless steel usage and open construction of tube 40 the heater is easily removable and insertable and good interchangeability is established. The savings in fabrication alone more than compensate for the more expensive materials used so that a net saving is realized in production costs as well as maintenance. The structure 42, 44 also performs the function of a conventional splash batlle limiting oil carryover to the jet nozzles 22.

The above-described advantages are made possible by the unique combination of parts presented in my pumpa simple boiler well for holding an oil pool, a horizontal rod heater in the pool, and a splash collection tray just above the pool. It is critical that the splash collection tray be located in the lower half of the vapor jet assembly and below the jet nozzles to maintain the requisite proximity to the oil pool and also to intercept splash that would otherwise be carried to the lowest nozzle 22 and lost through the foreline. Other features of the invention may be altered or omitted while retaining other distinct advantages of this invention and without departing from the broadest scope of the invention. For instance, heater tube 40 could be arranged vertically instead of horizontally as shown in the drawings. The annular splash baffie wall 44 could be an annular disc disposed horizontally and over the periphery of tray 42. Other variations will occur to those skilled in the art. It is therefore intended that the above description and accompanying drawing shall be read as illustrative and not in a limiting sense.

What is claimed is:

1. An oil diffusion pump comprising a vertically arranged annular pump body with a central axis and a lower capped end providing a boiler well for holding a pool of oil therein, heater means for boiling the oil in the well, a vapor jet assembly mounted axially in the pump forming a cover over the oil pool, the vapor jet assembly having a series of nozzles above the pool for discharging oil vapors outwardly from the vapor jet assembly, splash collection means comprising a cup-shaped member having a bottom and an annular, upwardly extending side wall with entrance means in the side wall above said bottom, said splash collection means being located axially within the vapor jet assembly immediately above the oil pool and below all the nozzles of the vapor jet assembly for receiving an essentially continuous supply of splashed oil from the boiling oil in the pool and supplying oil vapor to all said nozzles and constructed and arranged with respect to the pool to reach essentially the same temperature as the oil pool due to the direct impingement of splashed oil upon the bottom of said splash collection means to boil off oil in the tray to provide vapors for said nozzles, said splash collection means being further constructed and arranged within said vapor jet assembly for collection of splashed oil from said boiler pool via said entrance means. 7

2. The pump of claim 1 wherein the heater comprises a tube in the oil pool region of the pump with a heating element in the tube.

3. The pump of claim 2 wherein the tube is horizontally arranged and extends through the side wall of the pump body. I

4. The pump of claim 3 wherein the tube extends through the pump body to provide two open ends.

5. The pump of claim 4 with a fractionating tube extending essentially along the pump axis from the topmost nozzle of the vapor jet assembly to the cup-shaped mem- 4 her of said splash collection means and into the collected oil within said member.

6. The pump of claim 5 wherein the fractionating tube is enlarged at its lower end to encompass a large central region of the splashed oil in the splash collection means.

References Cited UNITED STATES PATENTS 2,437,897 3/1948 Stoltenberg et al. 230101 2,734,679 2/1956 Power 230-101 2,886,235 5/1959 Demon 230-101 3,165,255 1/1965 Landfors 230-101 3,258,196 6/ 1966 Knox et al. 230101 3,272,965 9/1966 Reichelt 230-10l X 3,302,864 2/1967 Nicolas 230-101 DONLEY J. STOCKING, Primary Examiner.

WARREN J. KRAUSS, Assistant Examiner. 

1. AN OIL DIFFUSION PUMP COMPRISING A VERTICALLY ARRANGED ANNULAR PUMP BODY WITH A CENTRAL AXIS AND A LOWER CAPPED END PROVIDING A BOILER WELL FOR HOLDING A POOL OF OIL THEREIN, HEATER MEANS FOR BOILING THE OIL IN THE WELL, VAPOR JET ASSEMBLY MOUNTED AXIALLY IN THE PUMP FORMING A COVER OVER THE OIL POOL, THE VAPOR JET ASSEMBLY HAVING A SERIES OF NOZZLES ABOVE THE POOL FOR DISCHARGING OIL VAPORS OUTWARDLY FROM THE VAPOR JET ASSEMBLY, SPLASH COLLECTION MEANS COMPRISING A CUP-SHAPED MEMBER HAVING A BOTTOM AND AN ANNULAR, UPWARDLY EXTENDING SIDE WALL WITH ENTRANCE MEANS IN THE SIDE WALL ABOVE SAID BOTTOM, SAID SPLASH COLLECTION MEANS BEING LOCATED AXIALLY WITHIN THE VAPOR JET ASSEMBLY IMMEDIATELY ABOVE THE OIL POOL AND BELOW ALL THE NOZZLES OF THE VAPOR JET ASSEMBLY FOR RECEIVING AN ESSENTIALLY CONTINUOUS SUPPLY OF SPLASHED OIL FROM THE BOILING OIL THE POOL AND SUPPLYING OIL VAPOR TO ALL SAID NOZZLES AND CONSTRUCTED AND ARRANGED WITH RESPECT TO THE POOL TO REACH ESSENTIALLY THE SAME TEMPERATURE AS THE OIL POOL DUE TO THE DIRECT IMPINGEMENT OF SPLASHED OIL UPON THE BOTTOM OF SAID SPLASH COLLECTION MEANS TO BOIL OFF OIL IN THE TRAY TO PROVIDE VAPORS FOR SAID NOZZLES, SAID SPLASH COLLECTION MEAN BEING FURTHER CONSTRUCTED AND ARRANGED WITHIN SAID VAPOR JET ASSEMBLY FOR COLLECTION OF SPLASHED OIL FROM SAID BOILER POOL VIA AID ENTRANCE MEANS. 